Process for preparing polycyclic dibasic acid



I ills United States Patent PROCESS FOR PREPARING POLYCYCLIC DIBASIC ACID Herbert K. Wiese and James H. McAteer, Cranford, N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application December 30, 1953, Serial No. 401,437

9 Claims. (Cl. 260-514) This invention relates to the production of alkali metal salts of polycyclic dicarboxylic acids and dicarboxylic acids resulting therefrom. More particularly, it is con cerned with an improved process for the production of allcali metal salts of dicarboxylic acids and the acids themselves, derived primarily from cyclodienes, such as cyclopentadiene and alkyl-substituted cyclodienes, such as methylcyclopentadiene, or from mixtures of dienes such as mixtures of cyclopentadiene and methylcyclopentadiene.

Starting with cyclopentadiene one obtains according to the process of this invention, dicyclopentadiene-3,7-dicarboxylic acid which was first prepared by Thiele: Berichte 34, 68 (1901) by treating cyclopentadiene with metallic potassium With subsequent gassing of the potassium cyclopentadiene with carbon dioxide at atmospheric pressure. Decomposition of the di-potassium salt with acid yielded the above dicyclopentadiene dicarboxylic acid. As he stated in a footnote, Thieles attempts to cause cyclopentadiene to react with sodium were unsuccessful.

Recently, Cohen and Mikeska (U. S. patent application Serial Number 268,122, filed January 24, 1952, now Pat- .ent No. 2,716,662, and assigned to applicants assignee) found that dicyclopentadiene dicarboxylic acid and dialkyl homologues of this acid are readily prepared in high yields by reacting metallic sodium which has been dispersed to a finely divided state, that is, to an average particle size of less than 50 microns in diameter, with monomeric cyclodienes, e. g., cyclopentadiene or alkyl cyclopentadiene in the presence of a small amount of an anhydrous alcohol activator, followed by conversion of the sodium cyclop'entadienes to acid by treatment with CO2 preferably at superatmospheric pressures up to 1000 p. s. i. g.

It has now been found that the yields of dicarboxylic acids resulting from the process of Cohen and Mikeska can be further increased by carrying out the reaction in such a manner that the alkali metal cyclodienyl is added to a reaction zone containing an inert hydrocarbon containing dissolved CO2. Preferably, a slurry of finely divided cyclodienyl sodium in an inert hydrocarbon such as xylene is prepared, as will be later explained, and added to a saturated solution of CO2 in the same or other inert hydrocarbon. The CO2 content of the solution should preferably be in excess over that required for the carboxylation of the metal cyclodienyl.

It has been found that, by utilizing the improved process of this invention, higher yields of dibasic acids are obtained, that undesirable acidic by-products are avoided, and that the process can be carried out at relatively low pressures, preferably less than 100 p. s. i'. g.

The reaction between the alkali metal cyclodienyl and the CO2 takes place at a temperature in the range of -50 to +250- C., preferably in the range of to 100 C. The CO: pressure can range from 1 to 1000 p.. s. i. g., the latter being the approximate tank pressure of CO2 available commercially. Pressures in the range of 1 to 100 p. s. i. g are preferred. The rate at which the alkali metal cyclodienyl is fed into the reactor is a 2,781,397 Patented Feb. 12, 1957 function of the carboxylation conditions such as CO2 pressure, temperature, and degree of agitation in the reaction zone. In brief, in order to realize the advantages of this process the carboxylation should be carried out in a manner such that an excess of CO2 is present at all times. The carboxylation can be carried out either batchwise or in a continuous type process. One way of carrying out the continuous type of operation consists in feeding the alkali metal cyclodienyl into the bottom of a reactor and continuously withdrawing carboxylated salt at the top of the reactor. The residence time can be varied depending on conditions such as those mentioned above from times less than one minute to approximately thirty minutes.

The alkali metal, e. g., sodium, potassium or lithium, employed in this reaction is in the form of a finely divided dispersion wherein the particles have an average size of less than 50 microns in diameter. Dispersion is obtained, for example, by mechanical means either with or without the aid of emulsifying or dispersing agents. An alcohol activator, e. g., substantially anhydrous alcohol, such as the low molecular weight aliphatic alcohols such as methanol, ethanol, isopropanol, etc., is preferably employed. Alcohols containing up to four carbon atoms per molecule are suitable but methanol, ethanol or isopropanol are preferred. The alcohol is employed in relatively small amounts, that is, less than 1 molecule based on the sodium and usually in amounts less than mole equivalent. The alcohol serves to activate the sodium either by removing surface impurities contained thereon or by forming small quantities of sodium alcoholate. Thus, if sodium is previously dispersed to a very finely divided state, preferably having a particle size of less than 50 microns in diameter, e. g., by mixing with xylene, heating to above the melting point of the sodium and then passing the mixture through a high-speed colloid mill and continuing the operation until the temperature falls below the solidification point of the sodium, one obtains the sodium in a activate the sodium either by removing, by means of solution, surface impurities or by forming small quantities of sodium alcoholate, immediate reaction may be obtained when a mole of monomeric cyclopentadieu'e is added to the dispersed sodium.

The hydrocarbon employed in the preparation of the slurry of alkali metal dispersion can be any inert aromatic hydrocarbon such as xylene, toluene, benzene, etc., such aliphatic materials as heptane, hexane, mixtures thereof, light naphthas, such'as Varsol, etc. These same hydrocarbons or any one of them are likewise suitable for use in the preparation of the solution of CO2 to which the alkali metal cyclodienyl is added in the carboxylation step of this invention.

The essential steps in the cyclodiene dibasic acid process are as follows with respect to sodium and cyclopentadiene:

(1) Preparation of sodium cyclodiene derivative:

2 2 Na 2 Hg (2) Carboxylation and dimerization of the sodium CsHsOH trace (3) Acidification and purification of the dibasic acid. To illustrate the efiectiveness of the processes of this invention runs have been carried out in which a slurry of cyclopentadienyl sodium prepared as aforesaid was" fed intermittently into a stainless steel turbo-mixer contain- Based on the proposed mechanism for the side reaction it is apparent that good CO2 contact must be provided in order to reduce the formation of undesirable byproducts. That this is realized by the procedure claimed is evident from the results obtained.

mg xylene saturated with CO under various pressures. Smce the carboxylauon of the cyclod1enyl sodium is The temperature of the reaction mixture ranged from 20 highly exothermic the older technique of carboxylation C. to 44 C. For comparative purposes a series of runs creates a problem of removing the heat ofreaction parwas made by the reverse procedure of adding CO under ticularly in large scale type operations. The improved pressure directly into the slurry of sodium cyclopenta- 1O process here claimed has the added advantage, in addidienyl. These results are as follows: tron to the advantages already recited, of providing bet- TABLE I Preparation of dicarboxylic acids from cyclopentadier'ze and methylcyclopentadiene Run No. 927 109 p 113 115 117 119 121 145 147 1011-15 103 149 1011-3 Cyelodiene used CPD 1 CPD 1: CPD 1: CPD .2 CPD 4 CPD 2 CPD z CPD 1: CPD MCPD h MCPD iti o P u-l- Charge:

Cyclodienyl sodium, moles 1. 43 1. 5 1. 5 1. 5 0. 51 0.68 1. 52 1. 50 1. 41- 1. 5 1. 33 1. 15 Suspended in xylene, ml. 1,000 000 600 600 200 300 600 600 600 750 600 600 Conditions of carboxylation:

Manner of carboxylation 1A 1 A l A 1A B 3 C 5 B 2 B 2 B 1 A 2 B 1 B CO: pressure, p. s. i. g. 40 500-1, 000 1-5 500-1, 000 40 1 40 80 500-850 40 40 CO2 contact time, hr 3 s 2. 75 3 0. 75 0. 5 0. 5 0. 5 0; 0. 5 Temperature, 0- 25-60 25-70 24-35 25-60 39-44 50to? -25 20-25 20-25 -60 20-25 20-24 Xylene in reactor, 1,000 750 1 1,250 750 800 800 800 500 800 750 800 800 Acids recovered, gm

Dicarboxylic 102. 5 111.5 03. 6 115.8 51.8 74. 3 149 148 149 149 164 12s By-product 20. 9 25. 4 24. 6 16. 6 1. s 1. 6 10. 5 10.0 9. 0 5. 3 5. 7 Acid No. on acids,

Diearboxylie d 8.96 s. 94 d 8. 94 d s. 91 9.10 8 97 d 9.00 d 8. 99 d 8. 90 c 7 65 7. 70 k 8.48 By-product 7. 24 7.12 7. 79 7. 90 8.10 7 79 s. 61 8.50 5. 88 6.16 6.00 Conversion of cyclodi mole percent:

Dicarboxylie c 64. 2 66. 5 55. 8 68.8 95.8 97. 9 88.5 88. 7 94.0 76. 0 96. 2 94. 4 By-product acid 10.6 12. 0 12.6 8. 7 2. 9 0. 2 6. 0 5. 6 3. 7 2. 4 3. 0 Total organic acids 74. 8 7s. 5 68. 4 77. 5 98.7 98. 1 94. 5 94.3 97.7 98.6 97.4 Non-organic acid 25. 2 21. 5 31. 0 22. 5 1. 3 1. 9 5. 5 5. 7 2. 3 1. 4 2. 6 Selectivity to diearboxylic acid, mole pcrcont 85.8 84.8 81.5 88.8 96.4 99.5 93.7 94.0 96 2 97.7 90.8

1 00: led into reactor containing the cyclodienyl sodium suspended in xylene.

- Cyclodicnyl sodium suspended in xylene fed into reactor containing inert liquid saturated with C01.

3 Cyclodienyl sodium fed into glass beaker containing xylene and excess solid Dry Ice.

9 Insoluble acid removed by filtration from acidified aqueous solution of carboxylated sodium salt.

b Mixture of acids soluble in filtrate. Acids contain carbonyl groups in addition to carboxyl groups. Based on solubility of product dicarboxylic acid in water, the amount of same expected in filtrate should be about 15% of total acids present.

B Calculated from acid number. I d Theoretical for dicyclopcntadiene dicarboxylic acid 9.08 meqJgm.

Theoretical for dimethyl dicyclopentadiene dicarboxylic acid 8.05 meqJgm.

1 Carbonyl No. 302 meqJgm. (=C=0).

a CPD=cyclopentadiene monomer.

b MCPD=methylcyclopentadiene monomer. 3 Based on total organic acids recovered.

Mixture consisting of wt. percent CPD and 50 Wt. percent MCPD.

k Theoretical for a 50-50 mixture 8.56 meqJgm. l Represents total volume of xylene.

Xylene used in making cyclodienyl sodium+xylene in reactor.

The data in Table I demonstrate that the CO2 solution 50 ter temperature control. The dicyclodiene dicarboxylic procedure (runs 119, 145, 147, 149, 1011-3, and 1011-15) results in a marked improvement in both the conversion of the sodium cyclodienyl to recoverable organic acids and selectivity to desired dicarboxylic acid. I

The exact composition of the undesirable organic acidic by-product normally obtained in the carboxylation reaction has not been determined. It has been observed, however, that this product contains carbonyl groups in addition to the carboxyl groups. Although the acid number is considerably lower than that of the desired dibasic acid, it is about 25 times more soluble in water and therefore can be separated from the reaction product. The color of this acidic by-product has ranged from yellow to black.

it is believed that the formation of the acidic byproduct, particularly the formation of carbonyl groups, may be due to the reaction of the cyclodienyl sodium with the carboxylated salt producing a derivative containing a group such as:

O Na

The latter on acidification liberates CO2, which was obacids produced by this invention are prepared from the sodium salts thereof by well-known simple hydrolysis procedures such as treatment of the salt with aqueous solutions of dilute mineral acid. Thus,- the salt is conveniently converted to the free acid by dissolving the salt in water and precipitating the acid by addition of dilute HCl or H2504 and recovering the acid crystals by filtration. The crude product can be recrystallized from approximately 50% aqueous methanol or approximately 70% aqueous acetic acid.

The dicyclopentadiene dicarboxylic acid has many useful properties industrially, e. g., higher alcohol esters of either the unsaturated acid or the fully hydrogenated acid are useful as solvents and plasticizers for resins and coating materials. It is also useful as a modifier for the production of alkyd resins when mixed with other suitable ingredients and may serve as a basic material for the production of polyester types of lubricants, as an ingredient of specialty greases and as asource of other compounds. g

Hydrogenated derivatives, e. g., dihydrodicyclopentadiene dicarboxylic acid, which areprepared by hydrogenation of the acid in the pre'senc e of a hydrogenation catalyst such as Adams platinum oxide are excellent replacements for phthalic anhydride in soybean-alkyd resin. Theacid itself is likewise a good substitute.

In addition to the use of relatively pure eyclopentadiene and methylcyclopentadiene in the above described process, good yields of high quality acids are also obtained by reacting mixtures of these two components. For example, suitable mixtures may contain 90% to 10% of cyclopentadiene and 10% to 90% of methlcyclopentadiene. In addition vapor phase steam cracked hydrocarbons boiling in the range of cyclopentadiene and methylcyclopentadiene containing paraflins and aromatics as diluents may also be employed. The acid products in such cases are mixtures of the dicyclopentadiene dicarboxylic acid, dimethyl dicyclopentadiene dicarboxylic acid, and methyldicyclopentadiene dicarboxylic acid.

Having described the invention in a manner such that it may be practiced by those skilled in the art, what is claimed is:

1. An improved process for producing an alkali metal salt of cyclodiene dicarboxylic acids which comprises feeding a cyclopentadienyl of an alkali metal into a body of inert liquid hydrocarbon containing an excess of dissolved CO2 in a reaction zone and recovering alkali metal cyclodiene dicarboxylic acid salt from the reaction zone.

2. A process for producing alkali metal salts of cyclodiene dicarboxylic acids which comprises reacting a finely divided alkali metal with a cyclopentadiene hydrocarbon to form an alkali metal cyclodienyl, feeding the alkali metal cyclodienyl into a body of inert hydrocarbon containing an excess of CO2, and recovering alkali metal cyclodiene diearboxylic acid from the reaction mixture.

3. A process according to claim 2 in which the alkali metal is sodium and in which the cyclodiene is selected from the group consisting of cyclopentadiene, methylcyclopentadiene and mixtures thereof.

4. An improved process for producing a cyclodiene dicarboxylic acid which comprises reacting a finely-divided alkali metal with a cyclodiene hydrocarbon selected from the group consisting of cyclopentadiene, methylcyclopentadiene and mixtures thereof in the presence of a small amount of an aliphatic alcohol activator to form an alkali metal cyclodienyl, feeding the alkali metal cyclodienyl into a body of inert liquid hydrocarbon containing dissolved CO2 in a reaction zone at a temperature between 50 and 250 C., the amount of dissolved CO2 present being in excess of the amount required for carboxylation of the metal cyclodienyl recovering alkali metal salt of cyclodiene diearboxylic acid from the reaction zone, and converting the salt to free acid by acidification.

5. Process according to claim 4 in which the finelydivided alkali metal has a particle size of less than 50 microns in diameter.

6. Process according to claim 4 in which the finelydivided alkali metal is dispersed in an inert hydrocarbon liquid.

7. Process according to claim 4 in which the inert hydrocarbon is saturated with CO2 under a pressure of 1 to 1000 p. s. i. g., and in which the reaction with CO2 occurs at a temperature in the range of 20 to 100 C.

8. Process for producing dicyclopentadiene dicarboxylie acid compounds which comprises adding a slurry of finely-divided sodium cyclopentadienyl in xylene to a solution of xylene saturated with CO2 under pressure of 1 to 1000 p. s. i. g. in a reaction zone at a reaction temperature between 20 and 100 C., the amount of dissolved CO2 present being in excess of the amount rerequired for carboxylation of the sodium cyclopentadienyl, and separating the sodium salt of dicyclopentadiene dicarboxylic acid from the reaction zone.

9. Process according to claim 8 in which the salt is hydrolyzed by treatment with dilute mineral acid to produce dicyclopentadiene dicarboxylic acid.

References Cited in the file of this patent Gilman et al.: J. A. C. 5., vol. 62, pp. 1301-2 (1940). 

1. AN IMPROVED PROCESS FOR PRODUCING AN ALKALI METAL SALT OF CYCLODIENE DICARBOXYLIC ACIDS WHICH COMPRISES FEEDING A CYLOPENTADIENYL OF AN ALKALI METAL INTO A BODY OF INERT LIQUID HYDROCARBON CONTAINING AN EXCESS OF DISSOLVED CO2 IN A REACTION ZONE AND RECOVERING ALKALI METAL CYCLODIENE DICARBOXYLIC ACID SALT FROM THE REACTION ZONE. 